Copper zinc tin sulfo-selenide (CZT(S,Se)) is a non-toxic, earth abundant kesterite material that is used as the light absorbing material for thin film photovoltaic devices. CZT(S,Se) has many advantages relative to other thin film photovoltaic devices but overall the efficiency is a little more than half that of copper indium gallium selenide (CIGSe), cadmium telluride (CdTe), and bulk silicon (Si) photovoltaic devices. The primary reason for this low efficiency is the abundance of bulk defects that arise during fabrication of the CZT(S,Se) material.
To circumvent this efficiency deficit, device simulations have shown that if the absorber thickness is reduced to 1 micrometer (μm) or below, and a high work function back contact is utilized, then electrostatic field effects can result in higher open circuit voltages (Voc) and hence a higher efficiency CZT(S,Se) device. However, a high degree of electron-hole recombination at the back contact works to lower Voc.
Therefore, improved CZT(S,Se) device configurations and techniques for the fabrication thereof that solve these efficiency and electron-hole recombination challenges would be desirable.